#SORRY I FORGOT TO EDIT THE POLL TO SAY MONOTREMATA INSTEAD OF X AND I CAN’T CHANGE IT NOW 😭

[bestanimal]

Round 3 - Mammalia - Monotremata

(Sources - 1, 2, 3, 4)

Our first and most ancient living order of mammals is Monotremata. There are five living species of monotreme: one Platypus (image 1) and four echidnas. These are the Short-beaked Echidna (Tachyglossus aculeatus) (gif below), Attenborough’s Long-beaked Echidna (Zaglossus attenboroughi) (image 4), the Western Long-beaked Echidna (Zaglossus bruijnii) (image 2), and the Eastern Long Beaked Echidna (Zaglossus bartoni) (image 3).

Monotremes have structural differences in their brains, jaws, digestive tract, reproductive tract, and other body parts, compared to many other mammals, though they are most often differentiated by the fact that they are the last remaining order of mammals to lay eggs. All living species lack teeth as adults, though platypuses have them as babies. All living species have spurs on their hind limbs, though they are vestigial in echidnas. In male platypuses they are attached to venom glands and contain venom powerful enough to kill predators as large as a dog. Monotremes have 400-40,000 electroreceptors on their snouts, depending on species, which they use to locate invertebrate prey buried beneath sediment. All living species of monotremes are indigenous to Australia and New Guinea, though Cretaceous species were also found in South America.

Monotremes possess five pairs of sex chromosomes and one of the X chromosomes resembles the Z chromosome of birds, suggesting that the two sex chromosomes of other mammals evolved after the split from the monotreme lineage. Like reptiles, monotremes have a cloaca, which is a single opening for both reproduction and waste removal. However, urine is excreted through the cloaca while semen passes through the male monotreme’s penis. The monotreme penis is similar to that of turtles and is covered by a preputial sac. Monotreme eggs are soft-shelled and leathery. They are retained for some time within the mother and receive nutrients directly from her, generally hatching within ten days after being laid. Newly hatched monotremes are called “puggles,” and are fetus-like, with relatively well-developed forelimbs that enable them to crawl around. Female monotremes do have mammary glands and nurse their young with milk, though they lack teats. Instead, mother monotremes lactate via pores in their skin, “sweating” out the milk. All five living species show prolonged parental care of their young, with low rates of reproduction and relatively long life-spans.

Monotremes arose in the Early Cretaceous. Some of the oldest known platypus-like fossils are Steropodon and Dharragarra of the Late Cretaceous. Our living platypus is also known from Pliocene fossils.

Propaganda under the cut:

Monotremes maintain a lower average temperature than most mammals, conserving energy by "switching off" their temperature regulation and going dormant in cold weather.

The tongues of long-beaked echidnas (genus Zaglossus) have sharp, tiny spines that help them capture their termite, ant, and worm prey. Since they have no teeth, they break down their food by grinding it between the bottoms of their mouths and their tongues.

Monotreme milk contains a highly expressed antibacterial protein not found in other mammals.

Monotremes are the only mammals (apart from the Guiana Dolphin [Sotalia guianensis]) known to have a sense of electroreception, and the Platypus's electroreception is the most sensitive of any monotreme.

In the American animated series Phineas and Ferb, the title characters own a pet bluish-green Platypus named Perry who, unknown to them, is a secret agent. Coincidentally, and unbeknownst to show creator Dan Povenmire at the time, real platypuses biofluoresce a similar cyan colour when seen under ultraviolet lighting!

The longest recorded lifespan for an echidna in human care was 50 years, with anecdotal accounts of wild individuals reaching 45 years.

Venom production rises among male Platypuses during the breeding season, and it may be used to assert dominance.

I’m really sorry about more penis talk but we’re all adults here I hope. So… male echidnas have a four-headed penis, covered in penile spines. During mating, the heads on one side "shut down" and do not grow in size; the other two are used to release semen into the female's two-branched reproductive tract. Each time it copulates, it alternates heads in sets of two. When not in use, the penis is retracted inside a preputial sac in the cloaca. During mating season, a female may be followed by a line or "train" of up to ten males, the youngest trailing last, with some males switching between lines.

In 1799, the first scientists to examine a preserved Platypus body deemed it a hoax made of several animals sewn together.

Echidnas are very timid. When frightened, they attempt to partially bury themselves and curl into a ball similar to a hedgehog. Strong front arms allow echidnas to dig in and hold fast against a predator pulling them from the hole.

The rarest species of monotreme is the critically endangered Attenborough's Long-beaked Echidna (Zaglossus attenboroughi). It had only been seen once in 1961 in the Cyclops Mountains of the Indonesian province of Papua. It was thought to be extinct until some of its "nose pokes" (holes from the echidna’s nose poked into the ground as it searches for earthworms) were found in the mountains during an expedition in 2007. Finally, in November 2023, the first video footage of a living individual was recorded (image 4).

The Platypus holds special meaning as a totem animal for the Watiwati people, who live along the Murray River.